1) Field
Embodiments relate to the field of semiconductor manufacturing and, in particular, to systems and methods for cleaning an electrostatic chuck (ESC) using bias RF pulsing.
2) Description of Related Art
As workpieces are processed in a plasma processing chamber, byproducts of the plasma process may be deposited on surfaces of the processing chamber, and exposed portions of the electrostatic chuck (ESC) that supports the workpiece during processing. The buildup of these byproducts may negatively affect the processing of subsequent workpieces. For example, the deposition of byproducts along sidewalls and the showerhead may result in the contamination of subsequently processed workpieces. Additionally, byproduct buildup between a insert ring and a sidewall of the ESC may result in helium leaks because subsequent workpieces may not sit flat on the ESC, VRF instability, and/or micro-arcing that produces an unstable plasma.
Accordingly, the processing chamber may need to be periodically cleaned in order to prevent the buildup of undesirable byproducts on the chamber surfaces. This cleaning process is typically implemented as an in-situ chamber clean that is often performed without a workpiece present on the ESC (i.e., a wafer-less in-situ chamber clean, or ICC). However, it has proven to be particularly difficult to remove the byproducts from between the ESC sidewall and the insert ring. For example, the gap between the ESC sidewall and the insert ring has a confined geometry that does not allow for effective cleaning. In order to drive the cleaning species into the gap between the ESC sidewall and the ring, some ICC processes include applying a constantly high DC bias to the ESC. However, this results in a high ion energy that damages the exposed ESC surface on which the workpiece sits. The damage to the ESC reduces the lifespan of the component and may result in dechucking, workpiece temperature drift, and other negative processing effects.
In some ICC processes, a protective coating may be applied to the ESC surface in order to protect the surface from damage. Once the cleaning is completed, the protective coating then must be removed as well. As such, this process increases the time needed to run the ICC. Additionally, if the protective coating is not completely removed, a workpiece may not sit properly on the ESC. This may produce results that are significantly similar to those described above with respect to the damaged ESC, and is therefore, undesirable as well.